Highly Oxidized States of Phthalocyaninato Terbium(III) Multiple‐Decker Complexes Showing Structural Deformations, Biradical Properties and Decreases in Magnetic Anisotropy

Presented here is a comprehensive study of highly oxidized multiple‐decker complexes composed of Tb$_{III}$ and Cd$_{III}$ ions and two to five phthalocyaninato ligands, which are stabilized by electron-donating n-butoxy groups. From X-ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl-shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species. From paramagnetic $^{1}$H NMR studies on the resulting series of triple, quadruple and quintuple-decker complexes, ligand oxidation leads to a decrease in the magnetic anisotropy, as predicted from theoretical calculations. Unusual paramagnetic shifts were observed in the spectra of the +2e charged quadruple and quintuple-decker complexes, indicating that those two species are actually unexpected triplet biradicals. Magnetic measurements revealed that the series of complexes show single-molecule magnet properties, which are controlled by the multi-step redox induced structural changes

Spin Dynamics Phenomena of a Cerium(III) Double-Decker Complex Induced by Intramolecular Electron Transfer

Switchable spin dynamic properties in single-molecule magnets (SMMs) via an applied stimulus have applications in single-molecule devices. Many SMMs containing heavy lanthanoid ions with strong uniaxial magnetic anisotropy have been reported to exhibit SMM characteristics in the absence of an external magnetic field. On the other hand, SMMs containing light lanthanoid cerium(III) (Ce3+) ions exhibit field-induced slow magnetic relaxation. We investigated the chemical conversion of a diamagnetic Ce4+ ion (4f0) to a paramagnetic Ce3+ ion (4f1) in Ce-phthalocyaninato double-decker complexes (TBA+[Ce(obPc)2]− (1) and TBA+[Ce(Pc)2]− (2)) which exhibit field-induced SMM behaviour due to a 4f1 system. The phthalocyaninato ligands with electron-donating substituents (obPc2− = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato) in 1 have a significant effect on the valence state of the Ce ion, which is reflected in its magnetic properties due to the mixed valence state of the Ce ion. Given that Ce double-decker complexes with π-conjugated ligands undergo intramolecular electron transfer (IET) to the Ce ion mixed valence state, characterised by a mixture of 4f0 and 4f1 configurations, we examined the dynamic disorder inherent in IET influencing magnetic relaxation.Advance Articleのため、巻号頁記載なし→2024.07.17 巻号頁を追記。 This article is licensed under a Creative Commons Attribution 3.0 Unported Licence

Terbium(iii) bis-phthalocyaninato single-molecule magnet encapsulated in a single-walled carbon nanotube

In this study, terbium(III) bis-phthalocyaninato single-molecule magnets (TbPc2 SMMs) were encapsulated in the internal nano space of single-walled carbon nanotubes (SWCNTs) for the first time. The magnetic and electronic properties of the TbPc2 SMM–SWCNT hybrids were investigated in detail by using dc and ac magnetic susceptibility measurements, TEM, SEM, STM, STS, etc. By arranging the TbPc2 SMMs in the one-dimensional internal nano spaces of SWCNTs, it is possible to investigate the essential SMM characteristics of TbPc2 without considering ligand field (LF) effects. In addition, it appears that the electron correlation between TbPc2 and the SWCNT can affect the electrotransport and/or electromagnetic properties. Furthermore, since the stable internal nano space of SWCNTs is used, it is thought that the density of SMMs in the SMM–SWCNT hybrid material can be controlled, and the hybrids should be usable as spin valves. Our strategy may pave the way for the construction of SMM–SWCNT hybrid materials

Relationship between the Coordination Geometry and Spin Dynamics of Dysprosium(III) Heteroleptic Triple-Decker Complexes

When using single molecule magnets (SMMs) in spintronics devices, controlling the quantum tunneling of the magnetization (QTM) and spin-lattice interactions is important. To improve the functionality of SMMs, researchers have explored the effects of changing the coordination geometry of SMMs and the magnetic interactions between them. Here, we report on the effects of the octa-coordination geometry on the magnetic relaxation processes of dinuclear dysprosium(III) complexes in the low-temperature region. Mixed ligand dinuclear Dy3+ triple-decker complexes [(TPP)Dy(Pc)Dy(TPP)] (1), which have crystallographically equivalent Dy3+ ions, and [(Pc)Dy(Pc)Dy(TPP)] (2), which have non-equivalent Dy3+ ions, (Pc2− = phthalocyaninato; TPP2− = tetraphenylporphyrinato), undergo dual magnetic relaxation processes. This is due to the differences in the ground states due to the twist angle (φ) between the ligands. The relationship between the off-diagonal terms and the dual magnetic relaxation processes that appears due to a deviation from D4h symmetry is discussed

Dysprosium Acetylacetonato Single-Molecule Magnet Encapsulated in Carbon Nanotubes

Dy single-molecule magnets (SMMs), which have several potential uses in a variety of applications, such as quantum computing, were encapsulated in multi-walled carbon nanotubes (MWCNTs) by using a capillary method. Encapsulation was confirmed by using transmission electron microscopy (TEM). In alternating current magnetic measurements, the magnetic susceptibilities of the Dy acetylacetonato complexes showed clear frequency dependence even inside the MWCNTs, meaning that this hybrid can be used as magnetic materials in devices

Metal-Organic Framework of Lanthanoid Dinuclear Clusters Undergoes Slow Magnetic Relaxation

Lanthanoid metal-organic frameworks (Ln-MOFs) can adopt a variety of new structures due to the large coordination numbers of Ln metal ions, and Ln-MOFs are expected to show new luminescence and magnetic properties due to the localized f electrons. In particular, some Ln metal ions, such as Dy(III) and Tb(III) ions, work as isolated quantum magnets when they have magnetic anisotropy. In this work, using 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic acid (H3TATB) as a ligand, two new Ln-MOFs, [Dy(TATB)(DMF)2] (1) and [Tb(TATB)(DMF)2] (2), were obtained. The Ln-MOFs contain Ln dinuclear clusters as secondary building units, and 1 underwent slow magnetic relaxation similar to single-molecule magnets

Dy(III) Single-Ion Magnet Showing Extreme Sensitivity to (De)hydration

A new mononuclear dysprosium(III)-cucurbit[6]uril complex has been synthesized and characterized structurally and magnetically. It exhibits single-ion magnet (SIM) behavior with two slow magnetic relaxation processes, which are very sensitive to the solvation degree of the sample. Depending on the amount and type of the solvent in the structure, it is possible to switch the slow magnetic relaxation of this compound between the temperature-independent and temperature-dependent regimes.X114234sciescopu

Mn^III(tetra-biphenyl-porphyrin)–TCNE Single-Chain Magnet via Suppression of the Interchain Interactions

A single-chain magnet (SCM) of [Mn­(TBPP)­(TCNE)]·4<i>m</i>-PhCl₂ (<b>1</b>), where TBPP^2– = <i>meso</i>-tetra­(4-biphenyl)­porphyrinate; TCNE^• – = tetracyanoethenide radical anion; <i>m</i>-PhCl₂ = <i>meta</i>-dichlorobenzene, was prepared via suppression of interchain interactions. <b>1</b> has a one-dimensional alternating Mn^III(porphrin)–TCNE^• –chain structure similar to those of a family of complexes reported by Miller and co-workers. From a comparison of the static magnetic properties of <b>1</b> with other Mn^III(porphyrin)–TCNE^• – chains, a magneto-structural correlation between the intrachain magnetic exchange and both the dihedral angle between the mean plane on [Mn­(TBPP)­(TCNE)] and Mn–NC was observed. The ac magnetic susceptibility data of <b>1</b> could be fit with the Arrhenius law, indicating that slow magnetic relaxation and ruling out three-dimensional long-range ordering and spin-glass-like behavior. The Cole–Cole plot for <b>1</b> was semicircular, verifying that it is an SCM. Therefore, <b>1</b> is an ideal single-chain magnet with significantly strong intrachain magnetic exchange interactions beyond the Ising limit

Multiple-decker phthalocyaninato dinuclear lanthanoid(III) single-molecule magnets with dual-magnetic relaxation processes

International audienceThe SMM behaviour of dinuclear Ln(III)-Pc multiple-decker complexes (Ln = Tb3+ and Dy3+) with energy barriers and slow-relaxation behaviour were explained by using X-ray crystallography and static and dynamic susceptibility measurements. In particular, interactions among the 4f electrons of several dinuclear Ln(III)-Pc type SMMs have never been discussed on the basis of the crystal structure. For dinuclear Tb(III)-Pc complexes, a dual magnetic relaxation process was observed. The relaxation processes are due to the anisotropic centres. Our results clearly show that the two Tb3+ ion sites are equivalent and are consistent with the crystal structure. On the other hand, the mononuclear Tb(III)-Pc complex exhibited only a single magnetic relaxation process. This is clear evidence that the magnetic relaxation mechanism depends heavily on the dipole-dipole (f-f) interactions between the Tb3+ ions in the dinuclear systems. Furthermore, the SMM behaviour of dinuclear Dy(III)-Pc type SMMs with smaller energy barriers compared with that of Tb(III)-Pc and slow-relaxation behaviour was explained. Dinuclear Dy(III)-Pc SMMs exhibited single-component magnetic relaxation behaviour. The results indicate that the magnetic relaxation properties of dinuclear Ln(III)-Pc multiple-decker complexes are affected by the local molecular symmetry and are extremely sensitive to tiny distortions in the coordination geometry. In other words, the spatial arrangement of the Ln(3+) ions (f-f interactions) in the crystal is important. Our work shows that the SMM properties can be fine-tuned by introducing weak intermolecular magnetic interactions in a controlled SMM spatial arrangement

Mn^III(tetra-biphenyl-porphyrin)–TCNE Single-Chain Magnet via Suppression of the Interchain Interactions

A single-chain magnet (SCM) of [Mn­(TBPP)­(TCNE)]·4<i>m</i>-PhCl₂ (<b>1</b>), where TBPP^2– = <i>meso</i>-tetra­(4-biphenyl)­porphyrinate; TCNE^• – = tetracyanoethenide radical anion; <i>m</i>-PhCl₂ = <i>meta</i>-dichlorobenzene, was prepared via suppression of interchain interactions. <b>1</b> has a one-dimensional alternating Mn^III(porphrin)–TCNE^• –chain structure similar to those of a family of complexes reported by Miller and co-workers. From a comparison of the static magnetic properties of <b>1</b> with other Mn^III(porphyrin)–TCNE^• – chains, a magneto-structural correlation between the intrachain magnetic exchange and both the dihedral angle between the mean plane on [Mn­(TBPP)­(TCNE)] and Mn–NC was observed. The ac magnetic susceptibility data of <b>1</b> could be fit with the Arrhenius law, indicating that slow magnetic relaxation and ruling out three-dimensional long-range ordering and spin-glass-like behavior. The Cole–Cole plot for <b>1</b> was semicircular, verifying that it is an SCM. Therefore, <b>1</b> is an ideal single-chain magnet with significantly strong intrachain magnetic exchange interactions beyond the Ising limit